The present invention relates generally to molded case circuit breakers and particularly to lug terminals or other terminal connectors used thereon. Still more particularly, this invention relates to insulators covering the lugs or terminal connectors, trapped to the circuit breaker by attachment of the lug or terminal to the circuit breaker terminal.
Circuit breakers are commonly mounted within an electrical enclosure or draw out unit to provide overcurrent protection to a circuit. A line side of the circuit breaker is connected to an electrical power line supplying electricity and a load side of the circuit breaker is connected to the circuit to be protected. In all circuit breakers, the separation of the breaker contacts due to a short circuit causes an electrical arc to form between the separating contacts. The arc causes the formation of relatively high-pressure gases as well as ionization of air molecules within the circuit breaker including carbon deposits. These high-pressure gases can cause damage to the breaker casing and the carbon deposits on the lugs and lug screws can lead to dielectric breakdown. The gases, therefore, must be vented from the circuit breaker enclosure. In addition, a phase-to-phase fault can occur if the arc gases from different phases are allowed to mix, and a phase-to-ground fault can occur if the gases contact the grounded enclosure. To avoid a phase-to-phase or phase-to-ground fault, gases vented from different phases must be kept separate from each other and away from the grounded enclosure until the ionization has dissipated. These high temperature gases must exit the circuit breaker enclosure in order to prevent the circuit breaker enclosure from becoming over-stressed. Ventilated circuit breakers provide openings within the circuit breaker enclosure to allow the ionized gases to exit the circuit breaker in a controlled manner.
During installation of a circuit breaker, terminal straps extending from either a line side or a load side of a circuit breaker must be connected to its source or load (such as to bus lines or cable lines). Connection may be accomplished by inserting a screw, or other rod-shaped connector, through a hole in the terminal strap and through an opening in a connector for the source or load. A nut, or equivalent receiving or tightening device, may then be attached to the screw for securing the connection between the terminal strap and the source or load.
It is known to provide a wiring connector or lug on the load terminal of a molded case circuit breaker. These wiring lugs have at least one wire-receiving opening in an end face. The opening is individually intersected by a threaded opening which intersects the wire-receiving opening at a right angle. A set screw in the threaded opening projects into the wire-receiving opening to clamp a wire in a respective opening. This lug permits power through the circuit breaker to be distributed to a load device downstream or received from a source upstream of the circuit breaker.
It is further known to provide a molded insulating terminal cover which attaches to and becomes an extension of the circuit breaker molded case to provide an insulating covering for the lug terminals. Molded insulating lug covers require the circuit breaker molded case to be suitably configured with cooperative attachment features to receive the molded such attachment features molded into the members of the molded case and cannot readily receive a retrofit lug terminal or other terminal connector, such as for a bus bar connection.
A differently configured molded insulating terminal cover is utilized in a bus bar terminal connection which attaches to and becomes an extension of the circuit breaker molded case to provide an insulating covering for bus bar terminal connections. These molded insulating lug covers also require the circuit breaker molded case to be suitably configured with cooperative attachment features to receive the molded such attachment features molded into the members of the molded case and cannot readily receive a retrofit lug terminal or other terminal connector.
It would be economically advantageous, to provide bus covers and lug covers for molded case industrial-rated circuit breakers which require no additional fastening means for holding the lug and bus covers to the circuit breaker enclosure while providing improved isolation of the lugs or terminals and corresponding terminal screws. Accordingly, one purpose of the invention is to describe both lug and bus covers for industrial-rated circuit breakers which are economically feasible for both factory as well as field-installation.